(1) Field of the Invention
This invention relates to an improved thermoplastic resin composition and a method for producing the same. The thermoplastic resin composition of the invention has excellent properties and is prepared by subjecting a mixture of an engineering plastic and a rubber material containing .alpha.,.beta.-unsaturated carboxylic acids or its derivative to dynamic heat treatment in the presence of a carbon radical inducing agent.
(2) Description of Prior Art
Although the engineering plastic is light in weight, it excels in thermal resistance and rigidity. Accordingly, the utility of the engineering plastic has been widened for structural materials in place of hitherto used metals. In the field of structural materials for automobiles and for electric and electronic parts and accessories, the improvement in physical properties such as impact resistance are required. For this reason, the improvement of the material by blending several kinds of rubber-like materials having functional groups or ethylene copolymer, has been proposed. For example, proposed in Japanese Patent Publication No. Sho 62-37671 is a composition comprising polycarbonate, polyester and acrylate rubber-like copolymer. In Japanese Patent Publication No. Hei 2-381 is proposed a composition comprising polyester and epoxy-containing olefin; in Japanese Patent Publication No. Sho 63-53225, a composition comprising polyester and olefin modified with unsaturated carboxylic acids; and in Japanese Laid-Open Patent Publication No. Hei 1-203459 (corresponding to U.S. Pat. No. 4,895,899), a composition comprising polyester, polycarbonate and rubber of ethylene-propylene non-conjugated diene-copolymer grafted with styrene-acrylonitrile resin.
However, there is no proposal to improve these compositions further by utilizing the radical reaction. In the conventional art, when the compatibility of a resin must be improved by the radical reaction among various blended materials, it is carried out in the presence of a radical forming agent such as organic peroxides and azo compounds. The resins which are cross-linked by a radical forming agent such as an organic peroxide, the thermoplasticity (fluidity, etc.) is lost by cross-linking of molecules. Therefore, it was necessary to add a component which is not cross-linked by an organic peroxide in order to avoid the loss of thermoplasticity (for example, Japanese Laid-Open Patent Publication No. Sho 63-30547). The reason why the above measure has not been taken is considered that it cannot always be applied to any kind of blended resins.
As compositions which are similar to the composition of the present invention containing bismaleimide compounds are exemplified by a resin composition which is prepared by melt-kneading several thermoplastic resins with maleimide compounds having unsaturated bonds (Japanese Patent Publication No. Sho 56-18613), a resin composition which is prepared by melt kneading a polyolefin resin, another resin having carboxyl groups in molecules and maleimide compounds (Japanese Laid-Open Patent Publication No. Hei 2-269751), and a resin composition which is prepared by melt kneading a polyamide, a modified polyolefin and a maleimide compound (Japanese Patent Publication No. Sho 62-179546). It has, however, not yet been tried to improve the engineering plastic positively by using a radical forming agent.
The inventors of the present application have proposed a method to modify a thermoplastic resin using a carbon radical inducing agent which hardly causes side reaction and is different from conventional vigorous radical forming gents such as organic peroxides (Japanese Laid-Open Patent Publication No. Hei 2-49065, corres. to U.S. patent application Ser. No. 290,362).